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Advanced Organic Chemistry: Infrared spectrum of methoxymethane

Interpreting the infrared spectrum of methoxymethane (dimethyl ether)

Doc Brown's Chemistry Advanced Level Pre-University Chemistry Revision Study Notes for UK IB KS5 A/AS GCE advanced A level organic chemistry students US K12 grade 11 grade 12 organic chemistry courses involving molecular spectroscopy analysing infrared spectra of methoxymethane

C2H6O CH3OCH3 infrared spectrum of methoxymethane wavenumbers cm-1 functional group detection fingerprint pattern identification of dimethyl ether doc brown's advanced organic chemistry revision notes 

Spectra obtained from a liquid film of methoxymethane. The right-hand part of the of the infrared spectrum of methoxymethane, wavenumbers ~1500 to 400 cm-1 is considered the fingerprint region for the identification of methoxymethane and most organic compounds. It is due to a unique set of complex overlapping vibrations of the atoms of the molecule of methoxymethane.

Methoxymethane (dimethyl ether) alcohols and ether structure and naming (c) doc b alcohols and ether structure and naming (c) doc b alcohols and ether structure and naming (c) doc b alcohols and ether structure and naming (c) doc b alcohols and ether structure and naming (c) doc b

Revision notes on the structure and naming (nomenclature) of aliphatic ALCOHOLS and ETHERS

Interpretation of the infrared spectrum of methoxymethane

The most prominent infrared absorption lines of methoxymethane

The C-H stretching vibrations for a O-CH3 group occur at wavenumbers 2830 to 2815 cm-1.

The C-O stretching vibrations for a CH2-O-CH2 grouping occur at wavenumbers 1150 to 1060 cm-1.

The absence of other specific functional group bands will show that a particular functional group is absent from the methoxymethane molecular structure.

See also comparing the IR, mass, 1H NMR and 13C NMR spectra of isomers of C2H6O below.

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Comparing the infrared, mass, 1H NMR and 13C NMR spectra of the 2 isomers of C2H6O

NOTE: The images are linked to their original detailed spectral analysis pages AND can be doubled in size with touch screens to increase the definition to the original ethanol (ethyl alcohol) and methoxymethane (dimethyl ether) image sizes.

INFRARED SPECTRA: Apart from the significant differences in the fingerprint region at wavenumbers 1500 to 400 cm-1, the most striking difference is the broad O-H stretching band ~3400 cm-1, found in the infrared spectrum of alcohols, but absent in the infrared spectrum of ethers. You can clearly see, in the infrared spectrum of methoxymethane, the complete absence of the O-H vibration absorption band.

MASS SPECTRA: Both ethanol and methoxymethane show some similarities in their mass spectra, but their base ion peaks are quite different - for ethanol it is m/z 31 and for methoxymethane it is m/z 45.

1H NMR SPECTRA: The 1H NMR spectra of ethanol and methoxymethane are quite significantly different. Ethanol gives 3 peaks in the proton ratio 3:2:1 (3 different chemical environments), whereas methoxymethane only gives one 1H chemical shift peak (all 6 protons in the same chemical environment).

13C NMR SPECTRA: The 13C NMR spectra of ethanol and methoxymethane are different. Ethanol gives two 13C resonances, but methoxymethane only one (2 different 13C chemical environments and a 13C single chemical environment).


Key words & phrases: C2H6O CH3OCH3 image and diagram explaining the infrared spectrum of methoxymethane, complete infrared absorption spectrum of methoxymethane, comparative spectra of methoxymethane, prominent peaks/troughs for identifying functional groups in the infrared spectrum of methoxymethane, important wavenumber values in cm-1 for peaks/troughs in the infrared spectrum of methoxymethane, revision of infrared spectroscopy of methoxymethane, fingerprint region analysis of methoxymethane, how to identify methoxymethane from its infrared spectrum, identifying organic compounds like methoxymethane from their infrared spectrum, how to analyse the absorption bands in the infrared spectrum of methoxymethane detection of functional groups in the methoxymethane molecule example of the infrared spectrum of a molecule like methoxymethane with a functional group  interpreting interpretation of the infrared spectrum of methoxymethane shows presence of functional group dimethyl ether


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